1. Field of the Disclosure
Embodiments of the present disclosure may include a light emitting device using plasma discharge, and more particularly, a light emitting device using plasma discharge capable of reducing discharge voltage and improving luminous efficiency.
2. Description of the Related Art
In a light emitting device using plasma discharge (hereinafter, referred to as a plasma-discharge light emitting device), the plasma discharge is generated by a direct-current (DC) or alternating-current (AC) voltage applied between two electrodes, ultraviolet (UV) light generated during the discharge process excites fluorescent materials, and an image is formed by using visible light emitting from the fluorescence materials. Among the plasma-discharge light emitting devices, there are plasma display panel (PDP) and a flat lamp which is used for a black-light of a liquid crystal display (LCD).
The plasma-discharge light emitting device is classified into DC and AC types. In the DC type light emitting device, all electrodes are exposed to a discharge space, and discharge is generated by electrical charges directly moving between electrodes. In the AC type light emitting device, at least one electrode is covered with a dielectric layer, and discharge is generated by wall charges instead of the electrical charges directly moving between the electrodes.
In addition, the plasma-discharge light emitting device is classified into facing and surface discharge types. In the facing discharge light emitting device, a pair of two sustaining electrodes provided on front and rear substrates, facing each other, and discharge is generated in a direction perpendicular to the substrates. In the surface discharge light emitting device, a pair of sustaining electrodes is provided on the same substrate, and discharge is generated in a direction parallel to the substrate.
Although it has high luminous efficiency, the facing discharge light emitting device has a disadvantage that its fluorescent layer can be easily deteriorated due to plasma. Therefore, the surface discharge light emitting device has been mainly used.
FIGS. 1 and 2 illustrate a conventional surface discharge plasma display panel. In FIG. 2, only the front substrate is illustrated in a 90°-rotated state in order to clearly show an internal structure of the plasma display panel.
Referring to FIGS. 1 and 2, the conventional plasma display panel includes rear and front substrates 10 and 20 facing each other. The space between the rear and front substrates 10 and 20 is a discharge space where the plasma discharge is generated.
A plurality of address electrodes 11 are provided on an upper surface of the rear substrate 10. The address electrodes 11 are buried in a first dielectric layer 12. A plurality of barrier ribs 13 partitioning the discharge space are provided on an upper of the first dielectric layer 12 to partition the discharge space. In addition, the barrier ribs 13 are provided in a predetermined interval on the upper surface of the first dielectric layer 12 in order to prevent electrical or optical crosstalk between the discharge cells 14. The discharge cells 14 are filled with a discharge gas which is generally a mixture of Ne and Xe. Fluorescent layers having a predetermined thickness are coated on inner walls of the discharge cells 14, that is, the upper surface of the first dielectric layer 12 and side surfaces of the barrier ribs 13.
The front substrate 20 is a transparent substrate, which is mainly made of glass capable of passing visible light. The front substrate 20 is coupled with the rear substrate 10 provided with the barrier ribs 13. On a lower surface of the front substrate 20, there are provided pairs of sustain electrodes 21a and 21b in a direction perpendicular to the address electrodes 11. The sustain electrodes 21a and 21b are mainly made of a transparent, conductive material such as indium tin oxide (ITO) capable of passing the visible light. On lower surfaces of the sustain electrodes 21a and 21b, there are provided bus electrodes 22a and 22b, made of metal, having a narrower width than those of the sustain electrodes 12a and 12b in order to reduce line resistance thereof. The sustain electrodes 21a and 21b and bus electrodes 22a and 22b are buried in a second dielectric layer 23, which is a transparent layer. A protective layer 24 is provided on a lower surface of the second dielectric layer 23. The protective layer 24 functions as preventing damage to the second dielectric layer 23 due to sputtered plasma particles and reducing discharge voltage by emitting secondary electrons. In general, the protective layer 24 is made of MgO.
In the plasma display panel, the luminous efficiency can be improved by increasing a Xe partial pressure. However, in this case, there is a problem of increase in the discharge voltage. In addition, the luminous efficiency can be improved by widening a distance between the sustaining electrodes 21a and 21b to elongate a discharge path. However, in this case, there is a problem of increase in the discharge voltage.